1. Field of the Invention
The present invention relates to an electron tube.
2. Related Background Art
U.S. Pat. No. 5,594,301 discloses a photomultiplier tube having a stem pin to be held in a manner penetrating through a stem made of borosilicate glass. It is thus not difficult to make a stem made of borosilicate glass having a coefficient of thermal expansion close to that of a metal material and a relatively low melting point hold a stem pin in a penetrating state while sealing so that vacuum holding is possible. However, when the stem is made of quartz having a smaller coefficient of thermal expansion than that of the metal material and a relatively high melting point, it is very difficult to provide a stem pin by a similar structure.